Zeolites are microporous, aluminosilicate materials commonly used as commercial adsorbents and catalysts. Zeolites owe their adsorbent capacity to their regular pore structure of molecular dimensions. This regular pore structure provides zeolites an ability to selectively sort molecules based primarily on a size exclusion process.
When in an acid form, zeolite materials are also capable of catalyzing certain reactions, such as oligomerization and isomerization of components of many olefinic streams. Further, when used to remove or reduce undesired species from a reactive olefinic stream, zeolitic materials are subjected to repeated harsh regeneration cycles that occur during the life of the adsorbent. The conditions of the regeneration cycles encourage catalytic activity of the adsorbent, which leads to diminished adsorbent capacity and limited life span due to coking.
Unfortunately, certain zeolite materials that are otherwise suitable for removal or reduction of certain undesired compounds that may be present in an olefinic stream, such as organic sulfur-containing species, are particularly susceptible to problems arising from reacting with components in the olefinic stream. For instance, ZnX is an 80% ion exchanged Zn-based X-type zeolite which contains about 15% Zn on a volatile free basis. ZnX shows excellent organic sulfur removal behavior when used as an adsorbent for olefin streams. However, ZnX also displays high reactivity with olefins in terms of isomerization and oligomerization, leading to significant problems with coking and shortened lifespan. Thus, ZnX's reactivity with olefins limits ZnX's utility as an adsorbent for use with olefinic streams.
Accordingly, it is desirable to provide zeolites with satisfactory adsorbent behavior but reduced reactivity for use with olefinic streams. In addition, it is desirable to provide methods and systems for using such zeolites. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background.